1. Field of the Invention
Liquid stable MDI prepolymers and liquid stable curative systems suitable for room temperature casting which yield high performance urethane elastomers.
2. Prior Art
A search of the prior art showed many prepolymers and many curatives, none of which were specifically adapted to room temperature casting for the production of high-performance urethane elastomers, especially such elastomers which have remarkable low-shrink characteristics, wherein both the prepolymer and the curative are liquid or semi-liquid and stable at room temperature, and wherein the curing can also be effected at room temperature, and much less with systems which are totally free of TDI and which rely solely on MDI as the isocyanate-providing ingredient of the prepolymer.
It is an object of the present invention to provide liquid stable MDI prepolymers and liquid stable curative systems which are specifically adapted for room temperature casting and which yield high performance urethane elastomers upon room-temperature curing, the elastomer itself, as well as commercial combinations of the prepolymer and its complementary curative, separately packaged but together as a single unit or kit. Other objects of the invention will become apparent hereinafter.
What we believe to be our invention, then, inter alia, comprises the following, singly or in combination:
A room-temperature liquid stable prepolymer (P) which is the reaction product of
a) methylene diphenylisocyanate or a prepolymer of methylene diphenylisocyanate and an about 500-1000 equivalent weight polytetramethylene ether glycol or polyoxypropylene/polyoxyethylene diol or triol having at least 21% residual NCO,
b) polytetramethylene ether glycol of about 500 to 1000 equivalent weight, and
c) a polyoxypropylene/polyoxyethylene triol or polyoxypropylene triol of about 1300 to 2000 equivalent weight,
the percentage by weight in the prepolymer (P) being about 32 to 72% of (a), about 52 to 22% of (b), and about 6 to 15% of (c), and the percentage of residual NCO in the prepolymer (P) being about 6 to 18% by weight,
the prepolymer (P) having a viscosity at room temperature of about 1200 to 26000 cps,
which prepolymer (P) is curable and castable at room temperature to yield a high-performance urethane elastomer;
such a prepolymer (P) wherein the percentage of residual NCO in the prepolymer (P) is about 11.5-13.5% by weight and wherein the prepolymer (P) has a room temperature viscosity of about 3500 to 5000 cps;
such a prepolymer (P) wherein a) is methylene diphenylisocyanate;
such a prepolymer (P) wherein c) is a polyoxypropylene/polyoxyethylene triol having an equivalent weight of about 1300 to 2000 or a polyoxypropylene triol having an equivalent weight of about 1300 to 2000;
such a prepolymer (P) wherein (a) is a liquid uretonimine-modified methylene diphenylisocyanate;
such a prepolymer (P) wherein b) has an equivalent weight of about 500;
such a prepolymer (P) wherein b) has an equivalent weight of about 1000;
such a prepolymer (P) wherein a) is a previously-prepared reaction product of methylene diphenylisocyanate and polytetramethylene ether glycol having an equivalent weight of about 500 to 1000;
such a prepolymer (P) wherein a) is a previously-prepared reaction product of methylene diphenylisocyanate and a polyoxypropylene/polyoxyethylene diol having an equivalent weight of about 500 to 1000;
such a prepolymer (P) which is curable at room temperature with an approximately stoichiometric equivalent of a liquid curative consisting essentially of the following components:
(1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene triol of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3-20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5%;
such a prepolymer (P) which is cured at room temperature with an approximately stoichiometric equivalent of a liquid curative consisting essentially of the following components:
(1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene triol of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3-20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5%;
such a cured prepolymer wherein the amounts of (4) and (5) in the curative are respectively 10-20 and 5-15% by weight;
such a prepolymer (P) which is curable at room temperature with an approximately stoichiometric equivalent of a liquid curative consisting essentially of the following components:
(1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene triol of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3-20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5% to give a cured urethane elastomer having the following properties after mixing and curing for seven days at room temperature:
such a prepolymer (P) wherein the percentage of residual NCO in the prepolymer (P) is about 11.5-13.5% by weight and wherein the prepolymer (P) has a room temperature viscosity of about 3500 to 5000 cps and is cured at room temperature with an approximately stoichiometric equivalent of a liquid curative consisting essentially of the following components:
(1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene triol of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3-20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5% and a room-temperature viscosity of about 300-50000 cps, to give a cured urethane elastomer having the following properties after mixing and curing for seven days at room temperature:
such a cured prepolymer wherein the amounts of (4) and (5) in the curative are respectively 10-20 and 5-15% by weight;
such a cured product wherein the prepolymer (P) is present in an up to about 13% stoichiometric excess with respect to the curative;
such a cured product wherein the prepolymer (P) is present in about a 2 to 7% stoichiometric excess with respect to the curative;
such a prepolymer (P) wherein the percentages by weight of a), b), and c) are respectively about 54%, about 36%, and about 10%;
such a prepolymer (P) cured with an approximately stoichiometric equivalent of a curative consisting essentially of (1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene triol of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 11.5 to 13.5% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively approximately 54%, 13%, 10%, 15%, 8%, 0.005% and 0.006%;
such a cured prepolymer (P) wherein the curative has a viscosity at room temperature of about 3000-5000 cps and a specific gravity of about 1.05-1.08;
such a cured product wherein the prepolymer (P) is present in an up to about 13% stoichiometric excess with respect to the curative;
such a cured product the prepolymer (P) is present in about a 2 to 7% stoichiometric excess with respect to the curative;
such a cured prepolymer (P) wherein the properties after mixing and curing for seven days at room temperature are as follows:
such a cured prepolymer (P) wherein the degassing aid is a silicone emulsion;
such a cured prepolymer (P) wherein the catalyst is a mixture of triethylene diamine and 2,3-dimethyltetrahydropyrimidine or bismuth neodecanoate;
such a cured prepolymer (P) wherein the degassing aid is a silicone emulsion and the catalyst is a mixture of triethylene diamine and 2,3-dimethyltetrahydropyrimidine or bismuth neodecanoate.
Moreover, a kit comprising the separately packaged prepolymer (P) and a separately packaged curative consisting essentially of (1) a polyoxypropylene/-polyoxyethylene diol of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene trial of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3 20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5%;
such a kit wherein the curative has a viscosity at room temperature of about 300-50000 cps and a specific gravity of about 1.02-1.15;
such a kit comprising the separately packaged prepolymer (P) wherein the percentage of residual NCO in the prepolymer (P) is about 11.5-13.5% by weight and wherein the prepolymer (P) has a room temperature viscosity of about 3500 to 5000 cps and a separately packaged curative consisting essentially of (1) a polyoxypropylene/-polyoxyethylene dial of about 1000 to 2000 equivalent weight, (2) a polyoxypropylene/-polyoxyethylene trial of about 1300 to 2000 equivalent weight, (3) a chain extender having an equivalent weight of about 25 to 125, (4) a room-temperature liquid stable prepolymer (P) having a 6 to 18% residual NCO, (5) a diluent, (6) a degassing aid, and (7) a urethane catalyst, the relative amounts by weight being respectively 30-90%, 3-20%, 5-30%, 0-30%, 0-15%, 0.001-0.05%, and 0.01-0.5% and a room-temperature viscosity of about 300-50000 cps;
such a kit wherein the amounts of (4) and (5) in the curative are respectively 10-20 and 5-15% by weight;
such a kit wherein the curative consists essentially of the stated components in the following approximate percentages: 54%, 13%, 10%, 15%, 8%, 0.005%, and 0.006% and has a viscosity at room temperature of about 3000 to 5000 cps and a specific gravity of about 1.05-1.08;
such a kit wherein the percentages by weight of a), b), and c) in the prepolymer are respectively about 54%, about 36%, and about 10%; and
such a kit wherein the degassing aid in the curative is a silicone emulsion and the catalyst is a mixture of triethylene diamine and 2,3-dimethyltetrahydropyrimidine or bismuth neodecanoate.
A. Prepolymer (P) Portion
The polyol components used in the prepolymer portion of the system are represented by polytetramethylene ether glycol or polyoxypropylene, polyoxyethylene or mixed polyoxypropylene/polyoxyethylene diols or triols having molecular weights between 1000 and 6000 and an OH-functionality of about 2.0 to 3.0. Representative polyol components are:
Polytetramethylene ether glycol having a molecular weight between about 1000 and 2800 and a functionality of about 2.0, such as PTMEG 2000 or an equivalent QO2000(trademark) or Terathane 2000(trademark). Other products which can be used include PTMEG 1000, Great Lakes QO1000(trademark), or DuPont Terathane 1000(trademark). Further alternates include polyoxypropylene, polyoxyethylene or mixed polyoxypropylene/polyoxyethylene diols with molecular weights from 1000 to 2000 with functionalities of about 2.0. Examples of these alternates include Arch Poly-G 20-56(trademark), Arch Poly-G 55-112(trademark), Bayer Multranol 3600(trademark), Lyondell Acclaim 2220(trademark), Dow Voranol 220-056(trademark), and other polyols familiar to one skilled in the art such as:
Polyether triols having a molecular weight of about 4200 to 6000 and a functionality of about 3.0 including low unsaturation polyethers, such as Lyondell Acclaim 6320(trademark). Other products which can be used include Arch Poly-G 85-28(trademark), Arch Poly-G 30-28(trademark), Arch Poly-L 385-29(trademark), or Dow Voranol 230-027(trademark). Further alternates include polyoxypropylene, polyoxyethylene or mixed polyoxypropylene/polyoxyethylene triols with molecular weights of 4200 to 6000 and functionalities of about 3.0, which will be familiar to one skilled in the art.
The isocyanate component used in the prepolymer portion of the system is diphenylmethane diisocyanate having a functionality of about 2.0-2.1. The prepolymer is based on pure methylene diphenylisocyanate (MDI) such as Mondur M(trademark) from Bayer or Rubinate 44(trademark) from Huntsman or their equivalent, or a previously prepared isocyanate-terminated prepolymer based upon MDI and a polytetramethylene ether glycol (PTMEG) of 1000 or 2000 molecular weight (MW). Examples of these prepolymers include, but are not limited to, Mondur ME230(trademark) from Bayer and Rubinate 1027(trademark) from Huntsman. Other isocyanate functional materials suitable for use include uretonimine-modified methylene diphenylisocyanates commonly referred to as Mondur CD(trademark) from Bayer, Rubinate 1680(trademark) from Huntsman, or Isonate 2143L(trademark) from Dow and other equivalents. We have also evaluated and found prepolymers based on methylene diphenylisocyanate reacted with polyoxyethylene/polyoxypropylene diols of 1000 and 2000 MW to be acceptable. These materials are known by such tradenames as Isonate 2181(trademark) from Dow, Mondur MP210(trademark) from Bayer, Rubinate 1209(trademark) and Rubinate 1790(trademark) from Huntsman.
The prepolymer advantageously has a room-temperature viscosity of about 1200 to 26000 cps. Especially when the percentage of residual NCO in the prepolymer is the preferred 11.5-13.5% NCO, a viscosity of 3500-5000 cps is also preferred.
B. Curative (C) Portion
Polyol components used in the curative portion of the system are polyoxypropylene, polyoxyethylene, or mixed polyoxypropylene/polyoxyethylene diols or triols having molecular weights between 2000 and 6000 and OH-functionality of about 2.0 to 3.0. Representative polyol components are:
Commercially available low unsaturation polyoxyethylene terminated polyoxypropylene polyether triols and diols having a molecular weights of about 2000 to 6000 and functionalities of between about 2.0 and 3.0, such as Lyondell Acclaim 6320(trademark) and Acclaim 2220(trademark). Other products which can be used include Arch Poly-L 385-29(trademark), Poly-L 255-50(trademark), Poly-G 85-28(trademark), 30-28(trademark), 55-56(trademark), Dow Voranol 220-028(trademark) and 230-027(trademark). Further alternates include polyoxypropylene, polyoxyethylene or mixed polyoxypropylene/polyoxyethylene diols and triols with molecular weights from 2000 to 6000 and functionalities of about 2.0 to 3.0 which will be familiar to one skilled in the art.
The curative portion advantageously has a room-temperature viscosity of about 300-50000 cps, especially 4000-5000 cps, and most advantageously a specific gravity of about 1.02 to 1.15 and especially 1.05-1.08.
The crosslinker: The crosslinkers or chain extenders have molecular weights between about 50 and 250 and hydroxyl functionality of about 2.0, and thus an equivalent weight of about 25 to 125, such as 1,4-BDO or MPDiol. Some examples are: butanediol, 2-methyl-1,3 propanediol, trimethylolpropane, glycerine, ethylene glycol based crosslinkers such as DEG (diethylene glycol) and TEG (triethylene glycol), propylene based crosslinkers such as DPG (dipropylene glycol) or any combination of these components or other known crosslinkers familiar to one skilled in the art.
The catalyst: Any effective urethane/urethane-inducing catalyst or catalyst combination of the type which is normally used for urethane production can be employed in an effective polyurethane-catalyzing amount. Tertiary amines and organometallic catalysts are especially suitable. Some examples of suitable catalysts are those containing tin, such as dibutyltindilaurate, bismuth, such as bismuth neodecanoate, or zinc, such as zinc octoate. Some examples of tertiary amines are: triethylene diamine, 2,3-dimethylhydropyrimidine, and N,Nxe2x80x2-dimorpholinodiethyl ether. An effective amount of the polyurethane-catalyzing catalyst to obtain the desired reaction profile and work life is employed. A metal catalyst works well for this product, but tertiary amines and catalyst combinations also provide acceptable products. Representative catalysts and catalyst combinations are utilized in the Examples which follow, and additional suitable catalysts are disclosed in our U.S. Pat. No. 5,554,713.
Prepolymer in the curative: A room-temperature liquid stable prepolymer (P) as defined earlier, namely, which is the reaction product of
a) methylene diphenylisocyanate or a prepolymer of methylene diphenylisocyanate and an about 500-1000 equivalent weight prepolymer of MDI and polytetramethylene ether glycol or polyoxypropylene/polyoxyethylene diol or triol having at least 21% residual NCO,
b) polytetramethylene ether glycol of about 500 to 1000 equivalent weight, and
c) a polyoxypropylene/polyoxyethylene triol or polyoxypropylene triol of about 1300 to 2000 equivalent weight,
the percentage by weight in the prepolymer (P) being about 32 to 72% of (a), about 52 to 22% of (b), and about 7 to 15% of (c), and the percentage of residual NCO in the prepolymer (P) being about 6 to 18% by weight,
the prepolymer (P) having a viscosity at room temperature of about 1200 to 26000 cps. Some examples of commercially available methylene diisocyanates are pure MDI and uretonimine-modified MDI. Amounts of prepolymer in the curative are: 0-30, preferably 10-20, and advantageously about 15 to 17% by weight of the curative.
Diluent: Any suitable urethane-compatible material including, but not limited to alkyl phthalates such as dioctylphthalate, diisobutylphthalate, allyl benzyl phthalate; butyrates such as isobutyl isobutyrate or 2,2,4-trimethyl-1,3 pentanediol diisobutyrate; phosphates such as triphenyl phosphate or tributyl phosphate; and adipates such as dioctyladipate. Further examples include dipropylene glycol dibenzoate, diethylene glycol dibenzoate, dimethyl glutarate, dimethyl adipate, and dimethyl succinate. The diluent can thus be any suitable urethane-compatible material including, but not limited to, phthalate, adipate, or phosphate-based diluents such as: diisobutylphthalate or isobutylbutyrate, good examples being Velsicol""s Benzoflex(trademark) 988SG or Solutia""s Santicizer(trademark) 160 or 261, or other materials familiar to one skilled in the art. Amounts of diluent in the curative are: 0-30, preferably 5-15, and advantageously about 7 to 9% by weight of the curative.
Degassing agent: Any degassing agent typically used in the industry to eliminate or reduce the formation of bubbles in polyurethane products. Typical materials containing silicone as surface tension depressing agents can be utilized. Some examples of these materials are: OSI""s SAG 47(trademark), Furane Products"" Airout(trademark), and Ciba-Giegy""s X-Air(trademark). Other bubble elimination agents known to users familiar with the art may also be employed.